Ultrastructural changes in the hypopharyngeal gland of Apis mellifera workers with age

Abstract

SummaryThe hypopharyngeal gland (HPG) of the honey bee worker is concerned with biosynthesis and secretion of royal jelly fed to the queen and brood, as well as enzymes that hydrolyse and convert nectar into honey. The effect of age on the ultrastructure of the HPG of Apis mellifera carnica worker was studied. The HPG is a bilobed gland located in the head, and consists of a group of acini without marks on their external surface. The acini open by means of intra-cytoplasmic ducts into a main channel with a mutual arrangement. Each acinus comprises 12–20 secretory cells correspond to the same number of intra-cytoplasmic ducts. In 3 day old workers, the cytoplasm is homogenous with no obvious secretion. In 9 day old workers, the cytoplasm differentiation and secretions start, and increase at the age of 15 days to reach the maximum in 21 day old workers. The secretions continue in massive amounts in 27 day old foragers even with signs of secretory cell degeneration. This regression of the secretory activity assures the flexibility of the HPG, which cope with the colony conditions. The number of secretory cells is nearly twice as high as has been previously recorded and does not change with age. This might be a modification in the gland due to the difference in the climate and vegetation of Egypt. This needs further study.